fuel

Gary C · Jun 20, 2009

I always (so far, only filled it up 4 times [

]) use super, but with no additives or lead replacement. I believe these engines were built to run without lead, but Uk fuel octane was a little higher in 89 than it is now, so super is probably better for it. There is a fuel quality switch on the ECU that can be adjusted to run on lower octane fuel, I suppose that could be set if you want to run normal with a large safety margin.

johne · Jun 20, 2009

i have a 3.2 cabrolet supersport. what is the best fuel for my engine . had a top end rebuild last year and was wondering if it is best to use super unleaded or normal or weather i should be using an addative such as redex or any other suggestion

totsnap · Jun 21, 2009

Have tried Optimax etc and noticed no diff in mpg or bhp.... usual U/L is all I use and the car is more than happy with it Have owned the car for 6 yrs and normal U/L has been fine, for road use. You could prob. measure the higher grades of U/L within track use tho'...... Just my opinion of couse!

Gary C · Jun 21, 2009

ORIGINAL: SP_CS With Vpower, Ultimate etc etc you need a few tank fulls to feel the benefit IMO I have Tesco 99 available nearby, my car loves it .... post rebuild CR is now 10.45:1, so Tesco or Vpower 99 only for me

The car does not have a knock sensor as far as I know, and therefore does not adjust for different fuel grades. Therefore octane needs to be high enough to avoid knock, but any higher (octane) grants no benefit. Different fuels do though have different specific calorific value so they can produce more energy and therfore power. I imagine that the margin to knock when the cars were released on UK fuels was large enough such that the small reduction is still within the safety margin, but as my car does not do many miles, filling up with super is no burden and makes me happier.

75pno · Jun 21, 2009

Had a 3.2 supersport for 5 yrs and used normal unleaded with no problems. 75 pno

adamtsobek · Jun 22, 2009

Normal U/L petrol did it for me, only once filled with the higher octane petrol but did not feel any difference. So save some money stick with the ordinary U/L Adam

Big_nige · Jun 22, 2009

Sainsburys boggo standard for mine. Tried higher octane stuff and noticed a marginal increase in MPG, but not enough to become anally retentive on what fuel I use.

twinny · Jun 22, 2009

Guys, our cars DME's are dumb as the engine does not have a knock sensor therefore the only way to gain any real benefit from 98+ RON fuel is to have the ECU remapped.

Gary C · Jun 22, 2009

ORIGINAL: twinny Guys, our cars DME's are dumb as the engine does not have a knock sensor therefore the only way to gain any real benefit from 98+ RON fuel is to have the ECU remapped.

Totally true, the only question is, how near to the knock limit did Porsche set the UK cars in the 80's and how much did octane drop in the later part of the decade (I had an Astra at the time, and it needed its timing retarded slightly to stop the rattling can of pins noise). I suppose experience is the key, no history of melting pistons or valves for the last 20 yrs so normal must be ok (just search scoobynet for fuel paranoia

)

johne · Jun 22, 2009

thanks for the advice.i had a 964 rs for 5 yrs and ran that on super all the time .but this is no track car.that 3.2 must be fun 371 bhp with a twist

twinny · Jun 22, 2009

ORIGINAL: johne .....that 3.2 must be fun 371 bhp with a twist

Yep

nathan 1981 930 G50 · Jun 22, 2009

Considering the low cost of fuel compared to all the other expenses I only use shells finest. Probably for short journeys it's a waste of time, but when the engine (especially the heads) get hot I think the better quality fuel is good insurance against detonation. Sitting in traffic seems to get my engine oil hotter than anything, even than on a track. If you've ever seen pictures of 100 piece rings you won't bother penny pinching on fuel IMO.

twinny · Jun 22, 2009

ORIGINAL: nathan 1981 930 G50 Considering the low cost of fuel compared to all the other expenses I only use shells finest. Probably for short journeys it's a waste of time, but when the engine (especially the heads) get hot I think the better quality fuel is good insurance against detonation. Sitting in traffic seems to get my engine oil hotter than anything, even than on a track. If you've ever seen pictures of 100 piece rings you won't bother penny pinching on fuel IMO.

+1. Still to get mine remapped to read the higher RON fuel, but run V-Power to control detonation better particularly on track days. Nathan- Running hot in UK traffic? - Have you got an oil cooler fan fitted? I run a fan + lower temp thermostat on the switch + bumper scoop and mine's fine.

captbasil · Jun 30, 2009

Tell me more about where to get an oil cooler fan, please!

nathan 1981 930 G50 · Jun 30, 2009

No oil cooler fan on my car, just the stock 'tube oil cooler' in the drivers side front wing. My car has never over heated, I was just pointing out that not moving is the only thing that gets my car up to temp. The later 3.2's have an oil cooler that is more like a 'normal cars' water radiator. These radiator type coolers also have a stone guard/cowl & a fan fitted to it that is thermostatically controlled from the temp of the oil. This can then blow out hot air and cool the radiator type cooler. Shop around for prices.

TopCarrera · Jul 13, 2009

ORIGINAL: twinny Guys, our cars DME's are dumb as the engine does not have a knock sensor therefore the only way to gain any real benefit from 98+ RON fuel is to have the ECU remapped.

Not totally true. Whilst any ignition timing advance featured within a remapped/chipped ECU may need a higher RON fuel to safely liberate the associated extra horses super unleaded fuels will IMHO still provide potential power/mpg benefits for a car with a standard ECU. Aside from the pre-detonation/knock factors (which may not be an issue for a standard car running on 95 RON) then even at quite modest compressions/timings/chamber temperatures etc .. super unleadeds will still burn more more smoothly and consistently and release a few more bhp than standard 95 RON grades.

twinny · Jul 14, 2009

ORIGINAL: TopCarrera

ORIGINAL: twinny Guys, our cars DME's are dumb as the engine does not have a knock sensor therefore the only way to gain any real benefit from 98+ RON fuel is to have the ECU remapped.

Click to expand...

Not totally true. Whilst any ignition timing advance featured within a remapped/chipped ECU may need a higher RON fuel to safely liberate the associated extra horses super unleaded fuels will IMHO still provide potential power/mpg benefits for a car with a standard ECU. Aside from the pre-detonation/knock factors (which may not be an issue for a standard car running on 95 RON) then even at quite modest compressions/timings/chamber temperatures etc .. super unleadeds will still burn more more smoothly and consistently and release a few more bhp than standard 95 RON grades.

TC wot you doing here![

] Ahh nit picking...you know what I meant. The DME can't read the higher octane fuel.

leesweeney · Jul 15, 2009

ORIGINAL: johne i have a 3.2 cabrolet supersport. what is the best fuel for my engine . had a top end rebuild last year and was wondering if it is best to use super unleaded or normal or weather i should be using an addative such as redex or any other suggestion

I like whisky and brandy. Mackay's whisky and Three Barrells brandy does the job of getting one inebriated but tastes like parafin so I don't drink it. Single malt and VSOP/XO all the way because it's better. It's a quality thing. Mobil One in the engine, VPower in the tank.

Gary C · Jul 15, 2009

Humm In theory, a fuel with a higher octane could also be of lower quality (though I'm not suggesting they actually are). I do recall it quoted that the calorific value of some high octane fuels being lower than a fuel with lower octane, and may liberate less energy, though the higher knock resistance means that a higher percentage is turned into mechanical energy. Octane is just one parameter in a fuels quality.